Based on article https://preslav.me/2023/06/14/golang-focus-on-the-happy-path-with-step-functions/

go-happy-path-by-steps.go

package main

import (
	"fmt"
)

type steps struct {
	dayOfTheWeek string
	greeting     string
	tasks        []string
	funcs        []stepFunc
}

type stepFunc func() error

func (s *steps) Next(f stepFunc) *steps {
	s.funcs = append(s.funcs, f)

	// return the step func to allow for chaining
	return s
}
func (s *steps) Do() error {
	for _, f := range s.funcs {
		if err := f(); err != nil {
			// stop the chain prematurely
			return err
		}
	}
	return nil
}

func (s *steps) startTheDay() error {
	// chekc if valid day of the week
	if s.dayOfTheWeek == "" {
		return fmt.Errorf("day of the week is not set")
	}
	fmt.Println("Hello " + s.dayOfTheWeek)
	return nil
}

func (s *steps) doTasks() error {
	fmt.Println("Today's tasks are:")
	for _, task := range s.tasks {
		fmt.Println(task)
	}
	return nil
}

func main() {
	// create a new steps struct
	s := &steps{
		dayOfTheWeek: "Monday",
		greeting:     "Hello",
		tasks: []string{
			"Run",
			"Swim",
			"Cycle",
		},
	}

	// chain the steps together and execute them
	err := s.Next(s.startTheDay).Next(s.doTasks).Do()
	if err != nil {
		fmt.Println(err)
	}
}